I am loading an image in my UITableViewCell using
NSData is an "opaque" data, so you cannot do much with it before converting it to something more "useful" (e.g., creating an
UIImage by means of it
-initWithData: method). At that moment you could enquiry the image size, but it would be late for you.
The only approach I see, if you really need knowing the image size before the image is fully downloaded, is implementing a minimal server-side API so that you can ask for the image size before trying to download it.
Anyway, why do you need to know the image size before it is actually downloaded? Could you not set the row height at the moment when it has been downloaded (i.e., from your request delegate method)?